What is the difference between CRMSDK tags and FreeMarker tags?
CRMSDK tags can only source the value of fields to the template so the output would have content specific to that of the customer record from which the email was sent.
FreeMarker adds more options in using the data sourced from the record by applying conditions, loops, operations, etc by using its program language syntax.
The FreeMarker manual can be found in http://freemarker.org/docs/.
Should I be able to add FreeMarker tags to my existing templates?
Templates can only be a CRMSDK Template (version 1.0) or Scriptable (version 2.0 Beta). Coding across these types of templates is not allowed by the system. If you have a CRMSDK Template (or a template created prior to version 2013.2), then you'll have to continue using CRMSDK tags or create a new one using FreeMarker tags, this time.
How can I make sure that the interpolations I use in my template correspond to the correct field IDs in the record? Do you have a table?
The best way to determine the corresponding FreeMarker code of standard and custom fields in NetSuite is to use the Insert Field dropdown menu in the Text Editor of the template.
There is something wrong with my FreeMarker syntax. It's not following the conditions I set, thus, the desired text do not appear in the customer's system email template. Why?
Check if you are using the tags right. For the complete reference, visit FreeMarker's website at http://freemarker.org/docs/.
When I edit standard and custom System Email Templates, I do not see an option to create a Scriptable Template. There is no 'New' option, too, when I go to Setup > Company > System Email Templates. Why?
To create a new System Email Template, navigate to Setup > Company > System Email Templates. At the bottom of the list, click the New Template button.